Effect of Vitamin B12 Supplementation to Hydrocabon Yeast on Growth of Broiler

Three experiments were conducted to evaluate the effect of hydrocarbon yeast grown on n-paraffin, as dietary protein source for broiler. The contents of crude protein, metabolizable energy and vitamin B12 in the yeast were 64%, 3.39kcal/g and 0.02μg/g on dry-basis, respectively.In Expt. 1, all of fish meal and part or all of soybean meal in the control ration were replaced by the yeast at the dietary yeast level of 10, 15 and 20%, respectively. Body weight gain of the broiler at 10 weeks of age was in inverse proportion to the dietary yeast level. The relationship could be well described by the following equation:y=2, 347-23.39x+162.9swhere, y is body weight gain (g), x is dietary yeast level (%) and s is a correction term for sex difference, being 1 for male and -1 for female.In Expt. 2, 4 factors, i.e. supplementation of either vitamin B12 or fish meal, effect of pelleting of yeast and assesment of total digestible nutrients of yeast, being either 66 or 77%, were studied on the effect to improve growth rate of broiler on hydrocarbon yeast. Supplementation of either vitamin B12 or fish meal was effective to improve growth rate of broiler. Since the effect of both vitamin B12 and fish meal was not additive, the effect of fish meal was suspected to be due to vitamin B12 content in it. Pelleting the yeast improved feed intake but it had little effect on growth rate. Total digestible nutrients in the yeast was assessed as 77%, i.e. 3.39kcal of metabolizable energy per g on dry-basis.In Expt. 3, effect of supplemented vitamin B12, L-lysine, glycine and extra DL-methionine which had been added already at 0.1% level in all of the experimental diets, was compared. Only the supplementation of vitamin B12 was effective to improve the performance of broiler, supporting the findings in Expt. 2. Actually, growth rate of the chicks on 15% yeast diet with supplementary vitamin B12 was almost identical to that on the control diet, of which main protein source was fish meal and soybean meal.It was concluded that hydrocarbon yeast is lacking in sulfur amino acids and vitamin B12, resembling soybean meal as poultry feed. Supplementation of 50μg of vitamin B12 or of corresponding amount of fish meal, and of 0.1% of DL-methionine to the diet containing 15% of the yeast was satisfactory. With the supplemontation, hydrocarbon yeast is an excellent protein source for broiler.